Drafting machine



Oct. 20, 1959 R. L. GENTRY DRAFTING MACHINE 2 Sheets-Sheet 1 Filed Oct.14, 1954 ill/ 11 117,

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2,908,977 DRAFTING MACHINE Ray L. Gentry,-Anderson, Ind. ApplicationOctober 14, 1954, Serial No. 462,305 '2 Claims. CI. 33-79 This inventionrelates to a drafting machine of the type in which a scale orstraight-edge is adjustably carried by an articulated arm for parallelmovement over a drafting table, that is, for movement in which thestraightedge is always in a constant orientation about a movable axisextending normal to the surface of the drafting table.

It is an object of my invention to provide in such a machine an improvedmeans for adjusting the scale carrier with respect to the arm, by whichthe angularity or orientation of the scale may be simply and easilyadjusted.

In carrying out my invention in a preferred embodiment, the articuatedarm may comprise a'pair of jointed links or struts extending from afixed support to a remote pulley whose axis may be considered as theorientation axis, with belts and pulleys which maintain the remotepulley in a constant orientation about that axis. The remote pulleycarries a calibrated index plate, in fixed relation thereto. A scalecarrier is fixed to the lower end of a sleeve or hollow shaft whichpasses concentrically upward through the oriented pulley and is providedat its upper end with a control handle by whichthe scale-carrier can'beadjusted angularly with respect to the index plate. A plunger isslidably received within the sleeve and normally protrudes through thehandle for actuation by the palm of the hand. The plunger provides alock actuator for an index lock which locks the scale-carrier to theindex plate in selected angular positions. The handle and plungerprovide onehand control. To change or set the angularity of the scale,the operator grasps the handle with one hand, depresses the plunger withthe palm of the same hand to release the lock, and then rotates thehandle to swing the scale carrier to the selected position ofangularity. He then releases the plunger to lock the scale in its newposition of orientation.

These and other features and objects of my invention will appear fromthe illustrative embodiment of my invention shown in the accompanyingdrawings. In such drawings:

Fig. l is a plan view of a drafting machine embodying the invention,shown mounted on a drafting board;

Figs. 2 and 3 are sections taken on the lines 22 and 33 respectively ofFig. 1;

Fig. 4 is a section through the scale-carrying head of the machine shownin Fig. 1; and

Fig. 5 is a bottom plan view of the scale-carrying head andscale-carrier.

The machine shown in the drawing comprises an articulated arm of thestrut and belt type, which is clamped to a drawing board by a clamp 11.The upper end of the clamp forms a fixed pulley 18 provided with a beltgroove 19 in its outer circumferential surface. The arm comprises aninner strut 12 and an outer strut 14. The inner strut 12 is carried by ahead 13 which has a central boss received within a set of needlebearings 22 so that the strut 12 will freely pivot about the axis ofUnitedStatcs Patent 0 the fixed pulley 18. At their adjoining ends, thestruts 12 and 14 are jointed to each other on an axis which is normallyparallel to the axis of the fixed pulley18. To this end, the two strutsare provided with heads which have coaxial central cylindrical bosses 20and 21, and these carry the inner races of two sets of needle bearingswithin the hub of an intermediate pulley 26. A bolt 15 secures the twoheads in place for frictional pivotal movement relative to each other,and the pulley 26 is freely rotatable with respect to the struts 12 and14. The outer end of the outer strut 14 carries a head 40 which forms acentral depending boss to support the inner race of a set of needlebearings on which a pulley 16 is journaled.

A belt 28 is engaged in the belt groove of the fixed pulley 18 and witha belt groove at the top of an intermediate pulley 26. A second belt 34is engaged in a belt groove at the bottom of the intermediate pulley 26and in a belt groove in the remote pulley 16. The belts maintain thethree pulleys in a constant orientation with respect to each other, andthus maintain the remote pulley 16 in a fixed orientation, the same asthat of the fixed pulley 18. Conveniently, the struts 12 and 14 areadjustable in length, to maintain a suitable tension on the belts'28 and34.

i The articulated arm structure described above is of a known type, andother types of articulated arms might be used. The present invention isprimarily concerned with the scale-carrying head at the free end of thearticulated arm and with its adjustment. The structure of such head isbest shown in Fig. 4.

As shown in Fig. 4, the constant-orientation pulley 16 carries a bottomplate 42 on which is mounted a fixed index plate 44. The hub of thepulley 16 and the central boss 38 of the'head 40 form a cylindricalopening to receive a concentric sleeve or hollow shaft 46. The lower endof the sleeve 46 is provided with a flange 47 to which is secured ascale carrier 48 for the desired scales or straight-edges 49. The upperend of the sleeve 46 carries a handle 50 by which the scale carrier 48may be rotated about the axis of the constant-orientation pul ley 16 tovary its angular position with respect to the index plate 44.

To lock the scale carrier 48 in selected positions of angularadjustment, the index supporting plate 42 is provided with a series ofholes 52 at suitable angular positions about the constant-orientationaxis of the pulley 16. Conveniently, the angular spacing between theholes is 15. A pin 54 carried on a tongue 58 mounted on the scalecarrier 48 is arranged to engage upwardly into the holes 52. As shown inFig. 5, the scale carrier 48 is provided with a slot 56 extendingradially from the axis of the sleeve 46. A tongue 58 is mounted in thisslot 56 and is hinged to the scale carrier 48 by a leaf spring 60, whichnot only provides for pivotal movement of the tongue 58, but biases thattongue upward. The lock pin 54 is carried by the tongue 58 in a positionto enter the index holes 52 from below.

Engagement and release of the pin 54 on the tongue 58 is controlled by aplunger 62 slidably mounted in the central sleeve 46. The upper end ofthe plunger carries a flanged button 64 which normally stands above thetop of the handle 50, and through which the plunger 62 is spring pressedupwardly by a spring 66. The lower end of the plunger 62 is providedwith an annular notch 68, conveniently formed between the bottom surfaceof the plunger 62 and the head of a screw 63. The free end of the tonguespring 60 is notched and received in the annular notch 68 of the plunger62, and the upward bias on the plunger 62 urges the tongue 58 upward toengage its pin 54 in an aligned index hole 52.

The bottom of the scale-carrying head is desirably pro Patented Oct 20,1959.

vided with a cup-shaped shoe 70, to support the head on V the surface ofthe drafting table and to provide clearance for movements of the plunger62. A slot in the wall .of the shoe provides clearance for pivotalmovement of the'tongue 58.

The drafting machine shown is extremely simple and convenient to use andto adjust. In preparing it for use, the struts and belts and pulleys ofthe articulated arm are adjusted to provide the desired orientation ofthe pulley 16 and the index plate or protractor 44 which it carries.Normally, the scale carrier 48 is calibrated to orient its scales orstraight-edges parallel with the edges of the drafting table 10, thescales may then be moved freely over the drafting table 10 and will bemaintained in that same orientation by the action of the articulated armand its belts. When it is desired to adjust the scales to some differentangular position, the draftsman simply grasps the handle 50 with onehnd, depresses the button 64 to release the scale carrier, and rotatesthe handle 50 as desired to swing the scales to the desired position.The depression of the button 64 depresses the plunger 62, which movesthe free end of the tongue 58 downwardly, causing that tongue to pivotsubstantially about its outer end and to lower the pin 54 out ofengagement with the aligned index hole 52. With that pin disengaged, thescale carrier is freely rotatable to a new position. If the desired newposition is one for which an index hole 52 is provided, that is, if itis say from the original position, the scale carrier will be guided tothe new position and locked in that new position by engagement of thepin 54 in the appropriate hole 52. To permit and cause that engagement,the operator simply releases the pressure on the central button 64within the handle 50. For intermediate positions, at which no indexholes 52 are provided, the pin 54 simply engages the flat bottom surfaceof the index-carrying plate 42. If it is desired to lock the scalecarrier 48 in such intermediate positions to adjustment, it may beprovided with a clamp nut 72 to clamp the edge of the index plate 44 tothe scale carrier 60.

I claim as my invention:

1. In a drafting machine in which a scale support is I able axis, ahollow scale carrier shaft journalled through said support and angularlyadjustable with-respectthereto by rotation on said axis,-a scale-carrierfixed to said shaft below said support and angularly adjustabletherewith, an adjustment handle fixed on the upper end of said shaft, aradially extending index plate carried by said support and having aplurality of axially extending index holes at angularly spaced pointsabout said axis, a lock-pin member extending radially below said indexplate and carrying an upstanding lock-pin for selective reception in theindex holes in said index plate, a leaf spring conueotionrbetween saidlock-pin member and said scale carrier and accurately fixing theposition of said lock-pin in the plane of said scale carrier, thefiexure of said spring permitting hinged movement of said lockpin memberto carry said lock-pin in a generally axial direction into and out ofsaid index holes, and an index 7 release plunger axially movable in saidhollow scale-carmaintained in constant orientation about a laterallymovrier shaft and operatively connected at its lower end to the lock-pinmember to actuate the same for releasing the lock-pin from the indexholes, the top end of said plunger extending through and above saidadjustment handle by which said scale-carrier shaft is rotatablyadjusted in said support, in position to be engaged and depressed by thepalm of the hand which grasps the handle to release the lock-pin andpermit the scale to be adjusted by rotation of the handle.

2. Drafting machine apparatus according to claim 1, in which the plungeris axially connected to the lock-pin member, with the addition of aspring between the plunger and the handle cooperating with theleaf-spring connection to bias the lock-pin to locking position.

References Cited in the file of this patent UNITED STATES PATENTS1,308,815 Simon July 8, 1919 2,256,445 Wiedem ann Sept. 16, 19412,370,971 Ketting Mar. 6, 1945 FOREIGN PATENTS 132,083 Sweden June 19,1951 1,004,723 France Nov. 28, 1951

